血管活性肠肽在屈光参差性弱视猫视皮层中的表达研究

The expression of vasoactive intestinal polypeptide in the visual cortex of the anisometropic amblyopia kittens

目的研究不同发育阶段屈光参差性弱视猫和正常猫视皮质17区血管活性肠肽（vasoactive intestinal polypeptide，VIP）表达变化，探讨VIP与视觉发育可塑性的关系及屈光参差对VIP的表达所产生的影响，为临床寻找有效预防和治疗弱视提供一种新的思路。方法在四川大学华西医院眼科应用普通4周龄健康家猫16只，按概率法随机分成正常对照组和实验组，每组各8只。实验组给予1％阿托品眼膏点右眼，每天2次造成弱视猫模型。在用药后3周、6周、9周、12周分别每组中各处死两只猫，分离出视皮质17区行HE染色及电镜观察、VIP免疫组织化学染色，并分别用光镜下计数和计算机图形分析软件得出结果。结果（1）免疫组化结果：同周龄组间比较：对照组免疫阳性细胞数和阳性细胞平均光密度值均高于同周龄实验组，P〈0．05，差异有统计学意义。实验组与对照组总体比较：随机区组方差分析，P〈0．05，差异有统计学意义，而且两组表达强度比较，秩和检验（t=47．5，P=0．021），认为两组表达强度有差异。（2）电镜和HE染色结果：HE染色光镜下可见实验组多数神经元呈圆形，正常对照组多数神经元呈多角形，不规则形。电镜下观察发现实验组视皮质神经元细胞核内染色质积聚，核皱缩变形，线粒体嵴变短、减少甚至消失，高尔基体、核糖体减少等细胞超微结构改变。结论异常视觉经验可导致VIP表达下降、视皮质神经元超微结构改变、功能下降，VIP在视觉发育过程中有重要作用。

Objective To investigate the expression changes of vasoactive intestinal polypeptide （VIP） in visual cortex of the normal and anisometropic amblyopia kittens during development at the field of tectology and neurocyto-molecular biology, and to research the relation between VIP and plasticity of visual system. These studies offer a basis of reference in preventing and treating aniso- metropic amblyopia. Methods Sixteen normal kittens （about 4-week of age） were divided into two groups randomly. Eight kittens were deduced amblyopia by monocular chronic atropinization; four （2 normal and 2 amblyopia） kittens were perused in every three weeks. Changes in number and optical density of immunopositive neurons of the expression of VIP-protein in the visual cortex area 17 were analyzed with immuno-cytochemistry. Results were obtained from slides examined under the light microscope and by computer image analysis. Transmission electron microscope was used to observe the ultrastructure of the visual cortex neurons, and a light microscope was used to observe the shapes of the neurons. Results Statistics showed that there were immunopositive neurons which appear as brown color in the visual cortex area 17. The number and optical density of VIP immunoreactive positive cells in normal kittens were higher than in amblyopia kittens at the same age （P 〈 0.05）. The degree of expression between these two groups was significantly different. Ultrastructurally, in the control group, the nuclear membrane of most neurons was discemable and chromatin was evenly distributed within the nucleus. Abundant cytoplasm and tubular-shaped mitochondria were observed. These ceils were also rich in Golgi bodies, ribosomes, and endoplasmic reticulum. In amblyopic kittens, nuclei of most neurons were aggregated, the number of ribosomes and Golgi bodies was reduced, mitochondria were swollen, and mitochondrial cristae were shortened or even absent. The endoplasmic reticulum was distended and reduced in magnitude. Conclusions Asymmetrical visual stimulation, such as anisometropia, reduces VIP expression and impairs the structure and functions of nerve cells in the visual cortex. VIP may play an important role in maintaining the plasticity of the visual system.